US20160083660A1 - Fcc process with an integrated secondary reactor for increased light olefin yields - Google Patents
Fcc process with an integrated secondary reactor for increased light olefin yields Download PDFInfo
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- US20160083660A1 US20160083660A1 US14/494,704 US201414494704A US2016083660A1 US 20160083660 A1 US20160083660 A1 US 20160083660A1 US 201414494704 A US201414494704 A US 201414494704A US 2016083660 A1 US2016083660 A1 US 2016083660A1
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- 150000001336 alkenes Chemical class 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title claims abstract description 64
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 230000001965 increasing effect Effects 0.000 title abstract description 9
- 239000003054 catalyst Substances 0.000 claims abstract description 118
- 238000005336 cracking Methods 0.000 claims abstract description 46
- 229930195733 hydrocarbon Natural products 0.000 claims description 36
- 150000002430 hydrocarbons Chemical class 0.000 claims description 35
- 239000004215 Carbon black (E152) Substances 0.000 claims description 24
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 18
- 238000000926 separation method Methods 0.000 claims description 18
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 12
- 238000000895 extractive distillation Methods 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 11
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 8
- 239000010457 zeolite Substances 0.000 claims description 8
- 238000004523 catalytic cracking Methods 0.000 claims description 7
- 150000001875 compounds Chemical class 0.000 claims description 7
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 6
- 229910021536 Zeolite Inorganic materials 0.000 claims description 6
- 238000011027 product recovery Methods 0.000 claims description 6
- 230000008929 regeneration Effects 0.000 claims description 6
- 238000011069 regeneration method Methods 0.000 claims description 6
- 230000005587 bubbling Effects 0.000 claims description 5
- 239000002904 solvent Substances 0.000 claims description 5
- -1 modernite Substances 0.000 claims description 4
- 238000010521 absorption reaction Methods 0.000 claims description 3
- 239000011959 amorphous silica alumina Substances 0.000 claims description 3
- UNYSKUBLZGJSLV-UHFFFAOYSA-L calcium;1,3,5,2,4,6$l^{2}-trioxadisilaluminane 2,4-dioxide;dihydroxide;hexahydrate Chemical compound O.O.O.O.O.O.[OH-].[OH-].[Ca+2].O=[Si]1O[Al]O[Si](=O)O1.O=[Si]1O[Al]O[Si](=O)O1 UNYSKUBLZGJSLV-UHFFFAOYSA-L 0.000 claims description 3
- 229910052676 chabazite Inorganic materials 0.000 claims description 3
- 229910052675 erionite Inorganic materials 0.000 claims description 3
- 239000012013 faujasite Substances 0.000 claims description 3
- 239000000376 reactant Substances 0.000 claims description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 abstract description 22
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 abstract description 21
- 238000004231 fluid catalytic cracking Methods 0.000 description 46
- 239000007789 gas Substances 0.000 description 14
- 238000004519 manufacturing process Methods 0.000 description 11
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 9
- 239000005977 Ethylene Substances 0.000 description 9
- 239000007788 liquid Substances 0.000 description 7
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- 239000000654 additive Substances 0.000 description 4
- 239000003921 oil Substances 0.000 description 4
- 125000004817 pentamethylene group Chemical class [H]C([H])([*:2])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[*:1] 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000004230 steam cracking Methods 0.000 description 4
- 125000000383 tetramethylene group Chemical group [H]C([H])([*:1])C([H])([H])C([H])([H])C([H])([H])[*:2] 0.000 description 4
- 150000001298 alcohols Chemical class 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- YNQLUTRBYVCPMQ-UHFFFAOYSA-N Ethylbenzene Chemical compound CCC1=CC=CC=C1 YNQLUTRBYVCPMQ-UHFFFAOYSA-N 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 230000002745 absorbent Effects 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- RWGFKTVRMDUZSP-UHFFFAOYSA-N cumene Chemical compound CC(C)C1=CC=CC=C1 RWGFKTVRMDUZSP-UHFFFAOYSA-N 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000012188 paraffin wax Substances 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical compound C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 238000007323 disproportionation reaction Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005194 fractionation Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000005649 metathesis reaction Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000004227 thermal cracking Methods 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G55/00—Treatment of hydrocarbon oils, in the absence of hydrogen, by at least one refining process and at least one cracking process
- C10G55/02—Treatment of hydrocarbon oils, in the absence of hydrogen, by at least one refining process and at least one cracking process plural serial stages only
- C10G55/06—Treatment of hydrocarbon oils, in the absence of hydrogen, by at least one refining process and at least one cracking process plural serial stages only including at least one catalytic cracking step
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
- C10G11/02—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils characterised by the catalyst used
- C10G11/04—Oxides
- C10G11/05—Crystalline alumino-silicates, e.g. molecular sieves
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
- C10G11/14—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts
- C10G11/18—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts according to the "fluidised-bed" technique
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
- C10G21/06—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents characterised by the solvent used
- C10G21/12—Organic compounds only
- C10G21/27—Organic compounds not provided for in a single one of groups C10G21/14 - C10G21/26
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G51/00—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more cracking processes only
- C10G51/02—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more cracking processes only plural serial stages only
- C10G51/026—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more cracking processes only plural serial stages only only catalytic cracking steps
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G70/00—Working-up undefined normally gaseous mixtures obtained by processes covered by groups C10G9/00, C10G11/00, C10G15/00, C10G47/00, C10G51/00
- C10G70/04—Working-up undefined normally gaseous mixtures obtained by processes covered by groups C10G9/00, C10G11/00, C10G15/00, C10G47/00, C10G51/00 by physical processes
- C10G70/041—Working-up undefined normally gaseous mixtures obtained by processes covered by groups C10G9/00, C10G11/00, C10G15/00, C10G47/00, C10G51/00 by physical processes by distillation
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
- C10G2400/20—C2-C4 olefins
Definitions
- the field of this invention relates to hydrocarbon cracking processes, and in particular the production of light olefins from cracking a heavy hydrocarbon feedstock
- ethylene and propylene are used in the production of polyethylene and polypropylene. These are among the most commonly manufactured plastics today.
- Other uses for ethylene and propylene include the production of other chemicals. Examples include vinyl monomer, vinyl chloride, ethylene oxide, ethylbenzene, cumene, and alcohols. This list is by no means exhaustive, but is representative of the versatility of ethylene and propylene.
- the production of ethylene and propylene is chiefly performed through the cracking of heavier hydrocarbons.
- the cracking process includes stream cracking and catalytic cracking of hydrocarbon feedstocks, such as naphtha, gas oils, and other hydrocarbon streams, as well as other sources of carbonaceous materials, such as recycled plastics and organic materials.
- a light olefins plant involves a very complex combination of reaction and gas recovery systems. Feedstock is charged to a thermal cracking zone in the presence of steam at effective conditions to produce a pyrolysis reactor effluent gas mixture. The mixture is then stabilized and separated into purified components through a sequence of cryogenic and conventional fractionation steps. Ethylene and propylene yields from steam cracking and other processes may be improved using known methods for the metathesis or disproportionation of C4 and heavier olefins, in combination with a cracking step in the presence of a zeolitic catalyst, as described, for example, in U.S. Pat. No. 5,026,935 and U.S. Pat. No. 5,026,936.
- Methanol in particular, is useful in a methanol-to-olefin (MTO) conversion process described, for example, in U.S. Pat. No. 5,914,433.
- MTO methanol-to-olefin
- the yield of light olefins from such a process may be improved using olefin cracking to convert some or all of the C4+ product of MTO in an olefin cracking reactor, as described in U.S. Pat. No. 7,268,265.
- Other processes for the generation of light olefins involve high severity catalytic cracking of naphtha and other hydrocarbon fractions. A catalytic naphtha cracking process of commercial importance is described in U.S. Pat. No. 6,867,341.
- shape selective additives are used in conjunction with conventional FCC catalysts containing Y-zeolites.
- the additives all have essentially the same selectivity characteristics.
- selectivity is limited, and the amount of propylene produced is only a function of the amount of additive used in the catalyst mixture.
- the propylene yield reaches a maximum at a crystalline shape selective zeolite content in the catalyst blend of approximately 10-12%.
- the FCC operation severity (temperature, catalyst/oil ratio, etc.) is increased to increase light olefin yield, but at the cost of increased undesirable yields of coke, dry gas, or methane and ethane, as well as C4 and C5 olefins.
- the final olefin yields are limited by the equilibrium distribution even at high severity.
- the present invention provides for a process to increase the yields of light olefins from a hydrocarbon feedstock.
- a first embodiment of the invention is a process for improving light olefin yields, comprising passing a hydrocarbon stream to an FCC reactor to generate an FCC effluent stream comprising light olefins; passing the FCC effluent stream to a product recovery unit to generate a first stream comprising light components, a second stream comprising C4 and C5 hydrocarbons, and a third stream comprising C6+ compounds; passing the second stream to an extractive distillation unit to generate a fourth stream comprising C4 and C5 olefins, and a fifth stream comprising paraffins; passing the fourth stream to a secondary reactor to generate a sixth stream comprising light olefins; and passing the sixth stream to the light olefins separation unit.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the secondary reactor is a bubbling bed reactor, a slow fluidized bed reactor or a fast fluidized bed reactor with partial regeneration.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing a catalyst to the secondary reactor, thereby generating a catalyst effluent stream.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the catalyst effluent stream to the FCC reactor.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the FCC reactor comprises a riser section, a catalyst separation section and a stripper section, and wherein the catalyst effluent stream is passed to the stripper section.
- the catalyst comprises a cracking catalyst selected from the group consisting of Y-zeolite, ZSM-5, ST-5, ZSM-11, ZSM-22, beta, erionite, ZSM-34, SAPO-11, non-zeolitic amorphous silica-alumina, faujasite, chabazite, modernite, and mixtures thereof.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the catalyst comprises ZSM-5.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing a regenerated catalyst stream to the FCC reactor, to generate an intermediate stream of catalyst and reactants; passing the intermediate stream to a reactor separation stage to generate the FCC effluent stream and an intermediate catalyst stream; passing the intermediate catalyst stream to a stripping section to generate a stripped catalyst stream; and passing the stripped catalyst stream to a regenerator to generate the regenerated catalyst stream.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the hydrocarbon stream is a VGO stream.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the extractive distillation unit comprises a selective olefin absorption process utilizing a solvent to generate the fourth stream comprising olefins and the fifth stream comprising paraffins.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the solvent is selected from the group consisting of NMP (n-methyl-2-pyrrolidone), DMF (dimethylformamide), THF (tetrahydrofuran), ACN (acetonitrile), and mixtures thereof.
- the solvent is selected from the group consisting of NMP (n-methyl-2-pyrrolidone), DMF (dimethylformamide), THF (tetrahydrofuran), ACN (acetonitrile), and mixtures thereof.
- a second embodiment of the invention is a process for improving light olefin yields, comprising passing a hydrocarbon stream to a cracking reactor, wherein the reactor includes a cracking catalyst, to generate a cracking effluent stream comprising light olefins; passing the cracking effluent stream to a separation unit to generate a first stream comprising C3 and lighter compounds, a second stream comprising C4 and C5 hydrocarbons, and a third stream comprising C6+ compounds; passing the second stream to an extractive distillation unit to generate a fourth stream comprising C4 and C5 olefins, and a fifth stream comprising paraffins; and passing the fourth stream to a secondary reactor, wherein the secondary reactor includes a cracking catalyst, to generate a sixth stream comprising light olefins.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the cracking reactor is a fluidized catalytic cracking reactor comprising a riser reactor.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a regenerated catalyst stream to the cracking reactor.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing the sixth stream to the light olefins separation unit.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a cracking catalyst to the secondary reactor to generate a secondary catalyst effluent stream.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing the catalyst effluent stream to the cracking reactor, thereby generating a cracking reactor catalyst effluent stream.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a regenerated catalyst stream to the cracking reactor thereby generating a spent catalyst effluent stream; and passing the spent catalyst effluent stream to a regenerator thereby generating the regenerated catalyst stream.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a fresh catalyst stream to the secondary reactor thereby generating a spent secondary catalyst stream; and passing the spent secondary catalyst stream to the cracking reactor stripping zone.
- An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the secondary reactor can comprise a bubbling bed reactor, a slow fluidized bed reactor, or a fast fluidized bed reactor, and wherein the secondary reactor utilizes the same catalyst, or a different catalyst, as the FCC reactor.
- FIG. 1 presents the FCC reactor and the secondary reactor for the process of enhancing light olefin production
- FIG. 2 presents the process with the product recovery unit for the recycle of the butenes and pentenes to the secondary reactor.
- Methods to increase the production include trying new catalysts, and other flow processes, but the primary source of light olefins is the cracking of a hydrocarbon stream through either steam cracking or fluidized catalytic cracking (FCC) reactor.
- the principal hydrocarbon stream is naphtha, but heavier hydrocarbon streams, such as a vacuum gas oil (VGO) can also be used.
- VGO vacuum gas oil
- the yields are not as great as with naphtha, and also cracking a heavier hydrocarbon stream also produces heavier by product streams.
- the present invention allows for the use of a heavier hydrocarbon stream, and is a new method that adds a smaller secondary reactor, wherein the catalyst for the reactor flows through the reactor and then into the FCC reactor.
- the integration will increase the propylene yield and is one of the objects of this invention.
- the process of the present invention is shown in FIG. 1 , and includes passing a hydrocarbon stream 8 to an FCC reactor 10 to generate an FCC effluent stream 12 .
- the FCC effluent stream 12 is passed to a product recovery unit 100 , as shown in FIG. 2 , to generate a first stream 202 comprising light components, a second stream 204 comprising C4 and C5 hydrocarbons and a third stream 194 comprising C6+ compounds.
- the second stream 204 is passed to an extractive distillation unit 210 to generate a fourth stream 212 comprising C4 and C5 olefins, and a fifth stream 214 comprising paraffins.
- the fourth stream 212 is passed to a secondary reactor 20 to generate a sixth stream 22 comprising light olefins.
- the sixth stream 22 is passed to the product recovery unit 100 .
- the secondary reactor 20 can comprise a bubbling bed reactor, a slow fluidized bed reactor, or a fast fluidized bed reactor with regeneration. With a fast fluidized bed reactor, the regeneration of the catalyst can be partial of total.
- the process further includes passing a catalyst stream 32 of fresh catalyst from the fresh catalyst feed hopper 30 to the secondary reactor 20 .
- a catalyst effluent stream 24 is generated during the movement of catalyst through the secondary reactor 20 .
- the catalyst effluent stream 24 is passed to the FCC reactor 10 , and enters the cycle of catalyst in the FCC system.
- the catalyst cycle is well known to those in the FCC arts, and comprises flowing a regenerated catalyst stream 42 through the FCC reactor 10 .
- the catalyst is separated from the product stream 12 and a spent catalyst stream 14 and passed to a regenerator 40 .
- the FCC reactor 10 comprises a riser section 52 , a catalyst separation section 54 , and a stripper section 56 .
- the spent catalyst from the separation section is passed to the stripper section to collect in a moving bed, where a gas is passed through the moving bed to remove residual hydrocarbons and other adsorbed materials that reduce the efficiency of the regenerator 40 .
- the regenerator 40 generates a regenerated catalyst stream 42 and passed the stream to the FCC reactor.
- the FCC reactor generates an intermediate stream leaving the FCC riser section 52 .
- the stream leaving the riser section 52 enters the separation stage 54 wherein an intermediate catalyst and an FCC effluent stream are separated.
- the intermediate catalyst stream enters the stripping section 56 to generate a stripped catalyst stream, and the stripped catalyst stream 14 is passed to the regenerator.
- the FCC reactor uses a catalyst, and the present invention uses the same catalyst for performing the cracking function.
- Suitable cracking catalyst are selected from one or more of Y-zeolite, ZSM-5, ST-5, ZSM-11, ZSM-22, beta, erionite, ZSM-34, SAPO-11, non-zeolitic amorphous silica-alumina, faujasite, chabazite and modernite.
- a combination catalyst can comprise two or more zeolites mixed into a common catalyst pellet, or can comprise a mixture of catalyst pellets of different types of catalytic materials.
- a preferred catalyst is ZSM-5.
- the product recovery unit 100 includes passing the FCC reactor effluent stream 12 and the secondary reactor effluent stream 22 to the main FCC column 110 .
- the main column 110 generate a heavy hydrocarbon stream 114 , and an overhead stream 112 comprising lighter components, including light olefins.
- the heavy hydrocarbon stream 114 is a residue stream from cracking and normally comprising a light cycle oil (LCO) stream.
- the overhead stream 112 is passed to a first separation vessel 120 to generate a first vapor stream 122 and a first liquid stream 124 . A portion of the first liquid stream 124 is used as reflux for the main FCC column 110 .
- the first vapor stream 122 is passed to a compressor 130 to generate a first compressed stream 132 .
- the first compressed stream 132 is passed to a second separation vessel 140 to generate a second vapor stream 142 and a second liquid stream 144 .
- the second vapor stream 142 is passed to a second compressor 150 to generate a second compressed stream 152 .
- the second liquid stream 144 and a portion of the first liquid stream 124 are passed to a naphtha splitter 160 .
- the naphtha splitter 160 generates a naphtha bottoms stream 164 comprising C7+ hydrocarbons, and a naphtha overhead stream 162 comprising C7 ⁇ hydrocarbons.
- the naphtha bottoms stream 164 can be passed to other process units in a refinery.
- the second compressed stream 152 is passed to a third separation vessel 170 to generate a third vapor stream 172 and a third liquid stream 174 .
- the third liquid stream 174 is passed to a deethanizer 180 to generate a deethanizer overhead 182 comprising C2 and lighter gases, and a deethanizer bottoms stream 184 comprising C3 and heavier hydrocarbons.
- the deethanizer bottoms stream 184 is passed to a depentanizer 190 to generate a depentanizer overhead stream 192 comprising C3 to C5 hydrocarbons, and a depentanizer bottoms stream 194 comprising heavier hydrocarbons.
- the depentanizer overhead stream 192 is passed to a depropanizer 200 to generate a depropanizer overhead stream 202 and a depropanizer bottoms stream 204
- the depropanizer overhead stream 202 comprises C3s and is passed to a C3 splitter to recover propylene.
- the depropanizer bottoms stream 204 comprises C4s and C5s. and is passed to an extractive distillation unit 210 .
- the extractive distillation unit 210 generates a paraffins stream 214 and an olefin stream 212 .
- the olefin stream 212 comprises C4 and C5 olefins and is passed to the secondary reactor 20 .
- the naphtha overhead stream 162 is passed to a light gas stripper 220 .
- the third vapor stream 172 is passed to the light gas stripper 220 .
- the depentanizer bottoms stream 194 can be passed to other process units in a refinery, or a portion, can be passed to the light gas stripper 220 .
- the bottom stream 222 of the light gas stripper 220 is recycled to the third separation vessel 170 .
- the light gas stripper overhead 224 can be passed to a sponge absorber 230 for removing contaminants to generate a lean gas stream 232 .
- the extractive distillation unit 210 comprises a selective olefin absorption process utilizing a solvent to generate the olefin stream 212 , and the paraffin stream 214 .
- Suitable absorbents for the extractive distillation unit can include one or more absorbents selected from n-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), tetrahydrofuran (THF), and acetonitrile (ACN).
- the flow configuration of the product recover unit 100 lends itself to the heat exchange of several streams leaving or entering the different separation columns. This is well known and not elaborated further here.
- This novel reactor configuration does not need additional catalyst for high propylene operation except the fresh makeup ZSM-5 catalyst for the FCC system.
- the ZSM-5 makeup catalyst is due to attrition losses in the FCC system during operation. However, this is a relatively small amount added per day (on the basis of total catalyst in the system) to maintain a constant level of activity.
- the makeup catalyst is first passed through the secondary reactor before passing into the FCC reactor. Since the spent catalyst will be regenerated in the FCC regenerator, catalyst regeneration process for this additional catalytic cracking process is optional.
- the separated reactor will allow the reaction condition to be optimized independently, so ethylene and propylene concentrations will not be constrained by the FCC riser condition. As a result, high ethylene and propylene yields of single pass can be achieved from this reactor.
- the catalyst density in this secondary reactor is much higher, and can be at least 10 times higher.
- the reactor size is much smaller than a second riser for the same purpose.
- the secondary bed reactor also allows a catalyst heat exchanger to work.
- the reactor like the FCC reactor, will be operated at low pressure, 170 to 210 kPa (absolute) and high temperature 580 C or above.
Abstract
A process for increasing the yields of propylene is presented. The process is an FCC process for producing light olefins, and utilizes a smaller secondary reactor that uses the same catalyst, or a different catalyst as in the FCC reactor. The FCC effluent is separated, and C4 and C5 olefins are recovered. The C4 and C5 olefins are passed to the secondary reactor for cracking to generate increased light olefin yields.
Description
- The field of this invention relates to hydrocarbon cracking processes, and in particular the production of light olefins from cracking a heavy hydrocarbon feedstock
- The production of light olefins, ethylene and propylene, are used in the production of polyethylene and polypropylene. These are among the most commonly manufactured plastics today. Other uses for ethylene and propylene include the production of other chemicals. Examples include vinyl monomer, vinyl chloride, ethylene oxide, ethylbenzene, cumene, and alcohols. This list is by no means exhaustive, but is representative of the versatility of ethylene and propylene. The production of ethylene and propylene is chiefly performed through the cracking of heavier hydrocarbons. The cracking process includes stream cracking and catalytic cracking of hydrocarbon feedstocks, such as naphtha, gas oils, and other hydrocarbon streams, as well as other sources of carbonaceous materials, such as recycled plastics and organic materials.
- A light olefins plant involves a very complex combination of reaction and gas recovery systems. Feedstock is charged to a thermal cracking zone in the presence of steam at effective conditions to produce a pyrolysis reactor effluent gas mixture. The mixture is then stabilized and separated into purified components through a sequence of cryogenic and conventional fractionation steps. Ethylene and propylene yields from steam cracking and other processes may be improved using known methods for the metathesis or disproportionation of C4 and heavier olefins, in combination with a cracking step in the presence of a zeolitic catalyst, as described, for example, in U.S. Pat. No. 5,026,935 and U.S. Pat. No. 5,026,936. The cracking of olefins in hydrocarbon feedstocks comprising C4 mixtures from refineries and steam cracking units is described in U.S. Pat. No. 6,858,133; U.S. Pat. No. 7,087,155; and U.S. Pat. No. 7,375,257.
- Currently, the majority of light olefins production is from steam cracking and fluid catalytic cracking (FCC). However, the demand for light olefins is growing and other means of increasing the amount of light olefins have been sought. Other means include paraffin dehydrogenation, which represents an alternative route to light olefins and is described in U.S. Pat. No. 3,978,150 and elsewhere. More recently, the desire for alternative, non-petroleum based feeds for light olefin production has led to the use of oxygenates such as alcohols and, more particularly, methanol, ethanol, and higher alcohols or their derivatives. Methanol, in particular, is useful in a methanol-to-olefin (MTO) conversion process described, for example, in U.S. Pat. No. 5,914,433. The yield of light olefins from such a process may be improved using olefin cracking to convert some or all of the C4+ product of MTO in an olefin cracking reactor, as described in U.S. Pat. No. 7,268,265. Other processes for the generation of light olefins involve high severity catalytic cracking of naphtha and other hydrocarbon fractions. A catalytic naphtha cracking process of commercial importance is described in U.S. Pat. No. 6,867,341.
- Another process for enhancing propylene yield is disclosed in U.S. Pat. No. 4,980,053, where a deep catalytic cracking process is disclosed. The process requires 5-10 seconds of contact time, and uses a mixture of Y-type zeolite and a pentasil, shape-selective zeolite. However, the process reports relatively high yields of dry gas.
- Other patents disclose short catalyst contact times, but do not recognize significant light olefin yields, such as in U.S. Pat. No. 5,965,012 which discloses an FCC process. The process has a catalyst recycle arrangement with a very short contact time of the feed with the catalyst. However, further cracking takes place in a contacting conduit where regenerated and carbonized catalyst contacts the feed, and not in the riser. Another FCC process is disclosed in U.S. Pat. No. 6,010,618 where there is a very short catalyst and feed contact time in the riser, and the cracked product is quickly removed below the outlet of the riser. Other patents, such as U.S. Pat. No. 5,296,131 disclose very short FCC catalyst contact times, but these processes are operated to improve gasoline production rather than production of light olefins.
- Other patents, U.S. Pat. Nos. 4,787,967, 4,871,446, and 4,990,314, disclose the use of two component catalysts used in FCC processes. The two component catalyst systems use a large-pore catalyst for cracking large hydrocarbon molecules and a small-pore catalyst for cracking smaller hydrocarbon molecules.
- To enhance propylene yields, shape selective additives are used in conjunction with conventional FCC catalysts containing Y-zeolites. The additives all have essentially the same selectivity characteristics. The problem with current catalysts is that selectivity is limited, and the amount of propylene produced is only a function of the amount of additive used in the catalyst mixture. The propylene yield reaches a maximum at a crystalline shape selective zeolite content in the catalyst blend of approximately 10-12%.
- To overcome this, the FCC operation severity (temperature, catalyst/oil ratio, etc.) is increased to increase light olefin yield, but at the cost of increased undesirable yields of coke, dry gas, or methane and ethane, as well as C4 and C5 olefins. The final olefin yields are limited by the equilibrium distribution even at high severity.
- Despite the variety of methods for generating light olefins industrially, the demand for ethylene and propylene is still increasing faster than new processes can provide. Moreover, further demand growth for light olefins is expected. A need therefore exists for new methods that can economically increase light olefin yields from existing sources of both straight-run and processed hydrocarbon streams.
- There is an increase in demand for light olefins, and in particular propylene. The present invention provides for a process to increase the yields of light olefins from a hydrocarbon feedstock.
- A first embodiment of the invention is a process for improving light olefin yields, comprising passing a hydrocarbon stream to an FCC reactor to generate an FCC effluent stream comprising light olefins; passing the FCC effluent stream to a product recovery unit to generate a first stream comprising light components, a second stream comprising C4 and C5 hydrocarbons, and a third stream comprising C6+ compounds; passing the second stream to an extractive distillation unit to generate a fourth stream comprising C4 and C5 olefins, and a fifth stream comprising paraffins; passing the fourth stream to a secondary reactor to generate a sixth stream comprising light olefins; and passing the sixth stream to the light olefins separation unit. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the secondary reactor is a bubbling bed reactor, a slow fluidized bed reactor or a fast fluidized bed reactor with partial regeneration. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing a catalyst to the secondary reactor, thereby generating a catalyst effluent stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the catalyst effluent stream to the FCC reactor. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the FCC reactor comprises a riser section, a catalyst separation section and a stripper section, and wherein the catalyst effluent stream is passed to the stripper section. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the catalyst comprises a cracking catalyst selected from the group consisting of Y-zeolite, ZSM-5, ST-5, ZSM-11, ZSM-22, beta, erionite, ZSM-34, SAPO-11, non-zeolitic amorphous silica-alumina, faujasite, chabazite, modernite, and mixtures thereof. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the catalyst comprises ZSM-5. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing a regenerated catalyst stream to the FCC reactor, to generate an intermediate stream of catalyst and reactants; passing the intermediate stream to a reactor separation stage to generate the FCC effluent stream and an intermediate catalyst stream; passing the intermediate catalyst stream to a stripping section to generate a stripped catalyst stream; and passing the stripped catalyst stream to a regenerator to generate the regenerated catalyst stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the hydrocarbon stream is a VGO stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the extractive distillation unit comprises a selective olefin absorption process utilizing a solvent to generate the fourth stream comprising olefins and the fifth stream comprising paraffins. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the solvent is selected from the group consisting of NMP (n-methyl-2-pyrrolidone), DMF (dimethylformamide), THF (tetrahydrofuran), ACN (acetonitrile), and mixtures thereof.
- A second embodiment of the invention is a process for improving light olefin yields, comprising passing a hydrocarbon stream to a cracking reactor, wherein the reactor includes a cracking catalyst, to generate a cracking effluent stream comprising light olefins; passing the cracking effluent stream to a separation unit to generate a first stream comprising C3 and lighter compounds, a second stream comprising C4 and C5 hydrocarbons, and a third stream comprising C6+ compounds; passing the second stream to an extractive distillation unit to generate a fourth stream comprising C4 and C5 olefins, and a fifth stream comprising paraffins; and passing the fourth stream to a secondary reactor, wherein the secondary reactor includes a cracking catalyst, to generate a sixth stream comprising light olefins. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the cracking reactor is a fluidized catalytic cracking reactor comprising a riser reactor. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a regenerated catalyst stream to the cracking reactor. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing the sixth stream to the light olefins separation unit. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a cracking catalyst to the secondary reactor to generate a secondary catalyst effluent stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing the catalyst effluent stream to the cracking reactor, thereby generating a cracking reactor catalyst effluent stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a regenerated catalyst stream to the cracking reactor thereby generating a spent catalyst effluent stream; and passing the spent catalyst effluent stream to a regenerator thereby generating the regenerated catalyst stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a fresh catalyst stream to the secondary reactor thereby generating a spent secondary catalyst stream; and passing the spent secondary catalyst stream to the cracking reactor stripping zone. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the secondary reactor can comprise a bubbling bed reactor, a slow fluidized bed reactor, or a fast fluidized bed reactor, and wherein the secondary reactor utilizes the same catalyst, or a different catalyst, as the FCC reactor.
- Other objects, advantages and applications of the present invention will become apparent to those skilled in the art from the following detailed description and drawings.
-
FIG. 1 presents the FCC reactor and the secondary reactor for the process of enhancing light olefin production; and -
FIG. 2 presents the process with the product recovery unit for the recycle of the butenes and pentenes to the secondary reactor. - The demand for light olefins, ethylene and propylene, continues to increase. Methods to increase the production include trying new catalysts, and other flow processes, but the primary source of light olefins is the cracking of a hydrocarbon stream through either steam cracking or fluidized catalytic cracking (FCC) reactor. The principal hydrocarbon stream is naphtha, but heavier hydrocarbon streams, such as a vacuum gas oil (VGO) can also be used. However, the yields are not as great as with naphtha, and also cracking a heavier hydrocarbon stream also produces heavier by product streams.
- Other processes for increasing propylene yields can include operating at higher severity, but these also need substantial amounts of ZSM-5 additive. Due to equilibrium constraints, the FCC reactor generates a substantial amount of other olefins, such as butenes and pentenes. This is in particular true for a typical Arabian Light VGO feedstock. While the current technology generates about 18 wt % of propylene, the process also generates about 20 wt % or more of butenes and pentenes. By recovering and passing the butenes and pentenes to a separate, but smaller reactor, the yields of propylene can be increased.
- The present invention allows for the use of a heavier hydrocarbon stream, and is a new method that adds a smaller secondary reactor, wherein the catalyst for the reactor flows through the reactor and then into the FCC reactor. The integration will increase the propylene yield and is one of the objects of this invention.
- The process of the present invention is shown in
FIG. 1 , and includes passing ahydrocarbon stream 8 to anFCC reactor 10 to generate anFCC effluent stream 12. TheFCC effluent stream 12 is passed to aproduct recovery unit 100, as shown inFIG. 2 , to generate afirst stream 202 comprising light components, asecond stream 204 comprising C4 and C5 hydrocarbons and athird stream 194 comprising C6+ compounds. Thesecond stream 204 is passed to anextractive distillation unit 210 to generate afourth stream 212 comprising C4 and C5 olefins, and afifth stream 214 comprising paraffins. Thefourth stream 212 is passed to asecondary reactor 20 to generate asixth stream 22 comprising light olefins. Thesixth stream 22 is passed to theproduct recovery unit 100. - The
secondary reactor 20 can comprise a bubbling bed reactor, a slow fluidized bed reactor, or a fast fluidized bed reactor with regeneration. With a fast fluidized bed reactor, the regeneration of the catalyst can be partial of total. - The process further includes passing a
catalyst stream 32 of fresh catalyst from the freshcatalyst feed hopper 30 to thesecondary reactor 20. Acatalyst effluent stream 24 is generated during the movement of catalyst through thesecondary reactor 20. Thecatalyst effluent stream 24 is passed to theFCC reactor 10, and enters the cycle of catalyst in the FCC system. The catalyst cycle is well known to those in the FCC arts, and comprises flowing a regeneratedcatalyst stream 42 through theFCC reactor 10. The catalyst is separated from theproduct stream 12 and a spentcatalyst stream 14 and passed to aregenerator 40. - The
FCC reactor 10 comprises ariser section 52, acatalyst separation section 54, and astripper section 56. The spent catalyst from the separation section is passed to the stripper section to collect in a moving bed, where a gas is passed through the moving bed to remove residual hydrocarbons and other adsorbed materials that reduce the efficiency of theregenerator 40. Theregenerator 40 generates a regeneratedcatalyst stream 42 and passed the stream to the FCC reactor. The FCC reactor generates an intermediate stream leaving theFCC riser section 52. The stream leaving theriser section 52 enters theseparation stage 54 wherein an intermediate catalyst and an FCC effluent stream are separated. The intermediate catalyst stream enters the strippingsection 56 to generate a stripped catalyst stream, and the strippedcatalyst stream 14 is passed to the regenerator. - The FCC reactor uses a catalyst, and the present invention uses the same catalyst for performing the cracking function. Suitable cracking catalyst are selected from one or more of Y-zeolite, ZSM-5, ST-5, ZSM-11, ZSM-22, beta, erionite, ZSM-34, SAPO-11, non-zeolitic amorphous silica-alumina, faujasite, chabazite and modernite. A combination catalyst can comprise two or more zeolites mixed into a common catalyst pellet, or can comprise a mixture of catalyst pellets of different types of catalytic materials. A preferred catalyst is ZSM-5.
- The
product recovery unit 100, as shown inFIG. 2 , includes passing the FCCreactor effluent stream 12 and the secondaryreactor effluent stream 22 to themain FCC column 110. Themain column 110 generate aheavy hydrocarbon stream 114, and anoverhead stream 112 comprising lighter components, including light olefins. Theheavy hydrocarbon stream 114 is a residue stream from cracking and normally comprising a light cycle oil (LCO) stream. Theoverhead stream 112 is passed to a first separation vessel 120 to generate afirst vapor stream 122 and a firstliquid stream 124. A portion of the firstliquid stream 124 is used as reflux for themain FCC column 110. Thefirst vapor stream 122 is passed to acompressor 130 to generate a firstcompressed stream 132. The firstcompressed stream 132 is passed to asecond separation vessel 140 to generate asecond vapor stream 142 and a secondliquid stream 144. Thesecond vapor stream 142 is passed to asecond compressor 150 to generate a secondcompressed stream 152. The secondliquid stream 144 and a portion of the firstliquid stream 124 are passed to anaphtha splitter 160. Thenaphtha splitter 160 generates a naphtha bottoms stream 164 comprising C7+ hydrocarbons, and anaphtha overhead stream 162 comprising C7− hydrocarbons. The naphtha bottoms stream 164 can be passed to other process units in a refinery. - The second
compressed stream 152 is passed to athird separation vessel 170 to generate athird vapor stream 172 and a thirdliquid stream 174. The thirdliquid stream 174 is passed to adeethanizer 180 to generate adeethanizer overhead 182 comprising C2 and lighter gases, and a deethanizer bottoms stream 184 comprising C3 and heavier hydrocarbons. The deethanizer bottoms stream 184 is passed to adepentanizer 190 to generate a depentanizeroverhead stream 192 comprising C3 to C5 hydrocarbons, and a depentanizer bottoms stream 194 comprising heavier hydrocarbons. The depentanizeroverhead stream 192 is passed to adepropanizer 200 to generate a depropanizeroverhead stream 202 and a depropanizer bottoms stream 204 The depropanizeroverhead stream 202 comprises C3s and is passed to a C3 splitter to recover propylene. The depropanizer bottoms stream 204 comprises C4s and C5s. and is passed to anextractive distillation unit 210. Theextractive distillation unit 210 generates aparaffins stream 214 and anolefin stream 212. Theolefin stream 212 comprises C4 and C5 olefins and is passed to thesecondary reactor 20. - The
naphtha overhead stream 162 is passed to alight gas stripper 220. Thethird vapor stream 172 is passed to thelight gas stripper 220. The depentanizer bottoms stream 194 can be passed to other process units in a refinery, or a portion, can be passed to thelight gas stripper 220. Thebottom stream 222 of thelight gas stripper 220 is recycled to thethird separation vessel 170. The light gas stripper overhead 224 can be passed to asponge absorber 230 for removing contaminants to generate alean gas stream 232. - The
extractive distillation unit 210 comprises a selective olefin absorption process utilizing a solvent to generate theolefin stream 212, and theparaffin stream 214. Suitable absorbents for the extractive distillation unit can include one or more absorbents selected from n-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), tetrahydrofuran (THF), and acetonitrile (ACN). - The flow configuration of the product recover
unit 100 lends itself to the heat exchange of several streams leaving or entering the different separation columns. This is well known and not elaborated further here. - This novel reactor configuration does not need additional catalyst for high propylene operation except the fresh makeup ZSM-5 catalyst for the FCC system. The ZSM-5 makeup catalyst is due to attrition losses in the FCC system during operation. However, this is a relatively small amount added per day (on the basis of total catalyst in the system) to maintain a constant level of activity. The makeup catalyst is first passed through the secondary reactor before passing into the FCC reactor. Since the spent catalyst will be regenerated in the FCC regenerator, catalyst regeneration process for this additional catalytic cracking process is optional. The separated reactor will allow the reaction condition to be optimized independently, so ethylene and propylene concentrations will not be constrained by the FCC riser condition. As a result, high ethylene and propylene yields of single pass can be achieved from this reactor.
- Unlike an FCC riser, the catalyst density in this secondary reactor is much higher, and can be at least 10 times higher. Hence, the reactor size is much smaller than a second riser for the same purpose. And, unlike a fixed bed reactor such as the olefin cracking process, where dual reactors loaded with special catalyst are needed to maintain a continuous operation during catalyst regeneration. The secondary bed reactor also allows a catalyst heat exchanger to work. The reactor, like the FCC reactor, will be operated at low pressure, 170 to 210 kPa (absolute) and high temperature 580 C or above. Therefore, total high C3=yield (26+ wt % on VGO) and C2=yield (10+ wt % on VGO) can be achieved in integrated system with typical VGO feedstock. Although the secondary bed reactor is integrated with the FCC unit, the FCC unit itself is a conventional FCC system. It can be operated with other modes such as gasoline mode by shutdown down this additional reactor.
- While the invention has been described with what are presently considered the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.
Claims (20)
1. A process for improving light olefin yields, comprising:
passing a hydrocarbon stream to an FCC reactor to generate an FCC effluent stream comprising light olefins;
passing the FCC effluent stream to a product recovery unit to generate a first stream comprising light components, a second stream comprising C4 and C5 hydrocarbons, and a third stream comprising C6+ compounds;
passing the second stream to an extractive distillation unit to generate a fourth stream comprising C4 and C5 olefins, and a fifth stream comprising paraffins;
passing the fourth stream to a secondary reactor to generate a sixth stream comprising light olefins; and
passing the sixth stream to the light olefins separation unit.
2. The process of claim 1 wherein the secondary reactor is a bubbling bed reactor, a slow fluidized bed reactor or a fast fluidized bed reactor with, or without, partial regeneration.
3. The process of claim 1 further comprising passing a catalyst to the secondary reactor, thereby generating a catalyst effluent stream.
4. The process of claim 3 further comprising passing the catalyst effluent stream to the FCC reactor.
5. The process of claim 4 wherein the FCC reactor comprises a riser section, a catalyst separation section and a stripper section, and wherein the catalyst effluent stream is passed to the stripper section.
6. The process of claim 1 wherein the catalyst comprises a cracking catalyst selected from the group consisting of Y-zeolite, ZSM-5, ST-5, ZSM-11, ZSM-22, beta, erionite, ZSM-34, SAPO-11, non-zeolitic amorphous silica-alumina, faujasite, chabazite, modernite, and mixtures thereof.
7. The process of claim 6 wherein the catalyst comprises ZSM-5.
8. The process of claim 1 further comprising:
passing a regenerated catalyst stream to the FCC reactor, to generate an intermediate stream of catalyst and reactants;
passing the intermediate stream to a reactor separation stage to generate the FCC effluent stream and an intermediate catalyst stream;
passing the intermediate catalyst stream to a stripping section to generate a stripped catalyst stream; and
passing the stripped catalyst stream to a regenerator to generate the regenerated catalyst stream.
9. The process of claim 1 wherein the hydrocarbon stream is a VGO stream.
10. The process of claim 1 wherein the extractive distillation unit comprises a selective olefin absorption process utilizing a solvent to generate the fourth stream comprising olefins and the fifth stream comprising paraffins.
11. The process of claim 10 wherein the solvent is selected from the group consisting of NMP (n-methyl-2-pyrrolidone), DMF (dimethylformamide), THF (tetrahydrofuran), ACN (acetonitrile), and mixtures thereof.
12. A process for improving light olefin yields, comprising:
passing a hydrocarbon stream to a cracking reactor, wherein the reactor includes a cracking catalyst, to generate a cracking effluent stream comprising light olefins;
passing the cracking effluent stream to a separation unit to generate a first stream comprising C3 and lighter compounds, a second stream comprising C4 and C5 hydrocarbons, and a third stream comprising C6+ compounds;
passing the second stream to an extractive distillation unit to generate a fourth stream comprising C4 and C5 olefins, and a fifth stream comprising paraffins; and
passing the fourth stream to a secondary reactor, wherein the secondary reactor includes a cracking catalyst, to generate a sixth stream comprising light olefins.
13. The process of claim 12 wherein the cracking reactor is a fluidized catalytic cracking reactor comprising a riser reactor.
14. The process of claim 12 further comprising:
passing a regenerated catalyst stream to the cracking reactor.
15. The process of claim 12 further comprising passing the sixth stream to the light olefins separation unit.
16. The process of claim 12 further comprising passing a cracking catalyst to the secondary reactor to generate a secondary catalyst effluent stream.
17. The process of claim 16 further comprising passing the catalyst effluent stream to the cracking reactor, thereby generating a cracking reactor catalyst effluent stream.
18. The process of claim 12 further comprising:
passing a regenerated catalyst stream to the cracking reactor thereby generating a spent catalyst effluent stream; and
passing the spent catalyst effluent stream to a regenerator thereby generating the regenerated catalyst stream.
19. The process of claim 18 further comprising:
passing a fresh catalyst stream to the secondary reactor thereby generating a spent secondary catalyst stream; and
passing the spent secondary catalyst stream to the cracking reactor.
20. The process of claim 12 wherein the secondary reactor can comprise a bubbling bed reactor, a slow fluidized bed reactor, or a fast fluidized bed reactor, and wherein the secondary reactor utilizes the same catalyst as in the FCC reactor.
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US20180002255A1 (en) * | 2014-12-30 | 2018-01-04 | Technip France | Method for improving propylene recovery from fluid catalytic cracker unit |
CN109135801A (en) * | 2017-06-16 | 2019-01-04 | 中国石油化工股份有限公司 | Catalyst cracking method and device |
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US6858133B2 (en) * | 1999-06-17 | 2005-02-22 | Atofina Research S.A. | Production of olefins |
US7462277B2 (en) * | 2002-07-24 | 2008-12-09 | Basf Aktiengesellschaft | Continuous method for separating a C4 cut |
US8889076B2 (en) * | 2008-12-29 | 2014-11-18 | Uop Llc | Fluid catalytic cracking system and process |
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US6858133B2 (en) * | 1999-06-17 | 2005-02-22 | Atofina Research S.A. | Production of olefins |
US7462277B2 (en) * | 2002-07-24 | 2008-12-09 | Basf Aktiengesellschaft | Continuous method for separating a C4 cut |
US8889076B2 (en) * | 2008-12-29 | 2014-11-18 | Uop Llc | Fluid catalytic cracking system and process |
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US20180002255A1 (en) * | 2014-12-30 | 2018-01-04 | Technip France | Method for improving propylene recovery from fluid catalytic cracker unit |
US10513477B2 (en) * | 2014-12-30 | 2019-12-24 | Technip France | Method for improving propylene recovery from fluid catalytic cracker unit |
CN109135801A (en) * | 2017-06-16 | 2019-01-04 | 中国石油化工股份有限公司 | Catalyst cracking method and device |
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